The prior art is replete with various types of locks using a key. Such keys are of various types in accordance with the kinds of locks, and the one side or both sides of such a key may be formed with concave grooves or the like. In the key making process, substantial time and cost are required.
On the other hand, when such a key is used the key should be rotated and unlocked in the hole of a lock, and such an operating process is very inconvenient. Accordingly, when an improper key is inserted in the lock, the key may be bent and the lock may be broken. Also, the concave portion on the sides of the key is limited in the changeable degree, and the formation of various concave portions is impossible. Unlocking operations by a similar key is very easy, and a pilfer-unlocking operation is very convenient. Accordingly, prior art lock mechanisms using a conventional key as very complex.
Also, a lock in the prior art has a device limiting a returning operation of a key lever and is disposed in a cylinder of a lock. The cylinder is mounted by a spring and a stopped portion which checks the unlocking position. In addition, rotation is conducted by inserting the key into a hole of the lock. Accordingly, the hole and the structures in the lock are very complicated and the process of manufacture of the lock is time consuming and cost is high.